Standard computer motherboards are widely available from various vendors. Because of their broad use, such boards are generally both highly reliable and inexpensive.
A typical standard motherboard contains a central processing unit (CPU), memory, and peripheral devices, connected by a bus, which complies with one of the Peripheral Component Interconnect (PCI) bus standards. Circuit boards with additional peripheral components, such as network adapter cards, may be plugged into the motherboard by means of bus slots on the bus. The bus slots are generally located at the rear of the motherboard in order to allow access to connectors on the plug-in circuit boards at the rear panel of the computer.
U.S. Pat. No. 5,592,366, whose disclosure is incorporated herein by reference, describes a front-loading computer/bus extender. An instrument includes a housing with a front opening in a first loading plane, and instrument receiving slots located in the housing. The chassis can be utilized as a stand-alone computer or it can operate as a bus extender for an existing computer. It is designed to allow top loading PC instrument cards to be front loaded.
U.S. Pat. No. 6,507,882, whose disclosure is incorporated herein by reference, describes an alternate use of computer storage device bays. A module is provided for installation in a drive bay of a computer and is adapted to accommodate expansion circuitry rather than the electromechanical devices conventionally installed in drive bays. A system interface board is provided for insertion into an expansion socket on the computer's motherboard and is connected to the module, thus interfacing the expansion circuitry to the computer.